The primary objective of this study is to develop an assessment tool that separates school and non-school influences on children's learning. Students' cognitive growth is shaped by both processes in and out of school and so an important limitation of past studies of schooling has been the difficulty in isolating its effects independent of non-school characteristics. The lack of experimental data means that most strategies for identifying characteristics of good schools are typically flawed because they do not fully account for the fact that the kinds of students attending schools with many resources are different than those attending resource-poor schools. As a result, it is unclear whether a school serving socioeconomically advantaged students, for example, can attribute its high test scores to hard-working teachers and efficient administrators, or to the students' advantaged non-school environments. Seasonal comparisons represent a powerful analytic technique for separating school and non-school effects. By using gains made during the summer, when school is not in session, as an estimate of the non-school effect, isolating the school effect can then be done for the academic year. This approach can be used to advance knowledge in two areas of schooling research: (1) the influence of schooling on inequality, (2) evaluating schools effectiveness.